What he hasn't done is struggle at the same level repeatedly. He was continually challenged, despite being on the slightly older end of the prospect age scale, and responded. I think you're losing that context by simply referring to overall numbers or "bad" years. In 2010, moved up from rookie ball to play 39 games at single-A with marginal results. Quickly pushed to high-A and continued that. In 2011, he started back in high-A and did well quickly, continuing that trend at AA. In 2012, he jumped to the majors and might not have been ready leading to struggles at both AAA and MLB. In 2013, he adjusted to MLB early in the year and did well. I'll buy the inconsistency argument more if he has a significantly sub-par year in 2014, but as is, I think you can contribute a fair amount of that track record to adjusting to new levels.